"""
Vector store abstraction layer for Honcho.
"""

from abc import ABC, abstractmethod
from dataclasses import dataclass, field
from typing import Any

from src.config import settings


@dataclass
class VectorRecord:
    """A single vector record to be stored in the vector store."""

    id: str
    embedding: list[float]
    metadata: dict[str, Any] = field(default_factory=dict)


@dataclass
class QueryResult:
    """A single result from a vector query."""

    id: str
    score: float  # Distance/similarity score (lower = more similar for cosine distance)
    metadata: dict[str, Any] = field(default_factory=dict)


class VectorStore(ABC):
    """
    Abstract base class for vector store implementations.

    All vector operations are namespace-scoped. Namespaces map to:
    - Document embeddings: {prefix}.{workspace}.{observer}.{observed} (per collection)
    - Message embeddings: {prefix}.{workspace}.messages (per workspace)

    Note: Period (.) is used as the delimiter since vector stores (Turbopuffer, LanceDB)
    only allow [A-Za-z0-9-_.] in namespace names, and period is not allowed in
    workspace/peer IDs (which only allow [A-Za-z0-9_-]).
    """

    namespace_prefix: str

    def __init__(self):
        """
        Initialize the vector store.
        """
        self.namespace_prefix = settings.VECTOR_STORE.NAMESPACE

    # === Namespace helpers ===
    def get_document_namespace(
        self, workspace_name: str, observer: str, observed: str
    ) -> str:
        """
        Get the namespace for document embeddings (per collection).

        Args:
            workspace_name: Name of the workspace
            observer: Name of the observing peer
            observed: Name of the observed peer

        Returns:
            Namespace string in format: {prefix}.{workspace}.{observer}.{observed}
        """
        return f"{self.namespace_prefix}.{workspace_name}.{observer}.{observed}"

    def get_message_namespace(self, workspace_name: str) -> str:
        """
        Get the namespace for message embeddings (per workspace).

        Args:
            workspace_name: Name of the workspace

        Returns:
            Namespace string in format: {prefix}.{workspace}.messages
        """
        return f"{self.namespace_prefix}.{workspace_name}.messages"

    # === Core operations ===
    @abstractmethod
    async def upsert(
        self,
        namespace: str,
        vector: VectorRecord,
    ) -> None:
        """
        Upsert a single vector into the store.

        Args:
            namespace: The namespace to store the vector in
            vector: VectorRecord containing id, embedding, and optional metadata
        """
        ...

    @abstractmethod
    async def upsert_many(
        self,
        namespace: str,
        vectors: list[VectorRecord],
    ) -> None:
        """
        Upsert multiple vectors into the store.

        Args:
            namespace: The namespace to store the vectors in
            vectors: List of VectorRecord objects to upsert
        """
        ...

    @abstractmethod
    async def query(
        self,
        namespace: str,
        embedding: list[float],
        *,
        top_k: int = 10,
        filters: dict[str, Any] | None = None,
        max_distance: float | None = None,
    ) -> list[QueryResult]:
        """
        Query for similar vectors.

        Args:
            namespace: The namespace to query
            embedding: The query embedding vector
            top_k: Maximum number of results to return
            filters: Optional metadata filters
            max_distance: Optional maximum distance threshold (cosine distance)

        Returns:
            List of QueryResult objects, ordered by similarity (most similar first)
        """
        ...

    @abstractmethod
    async def delete_many(self, namespace: str, ids: list[str]) -> None:
        """
        Delete multiple vectors from the store.

        Args:
            namespace: The namespace containing the vectors
            ids: List of vector identifiers to delete
        """
        ...

    @abstractmethod
    async def delete_namespace(self, namespace: str) -> None:
        """
        Delete an entire namespace and all its vectors.

        Args:
            namespace: The namespace to delete
        """
        ...


# Singleton instance
_vector_store_instance: VectorStore | None = None


def _create_vector_store() -> VectorStore:
    """
    Create a new vector store instance based on configuration.

    Returns:
        The vector store instance based on configuration.

    Raises:
        ValueError: If the configured vector store type is invalid.
    """
    store_type = settings.VECTOR_STORE.TYPE

    if store_type == "turbopuffer":
        from src.vector_store.turbopuffer import TurbopufferVectorStore

        return TurbopufferVectorStore()
    elif store_type == "lancedb":
        from src.vector_store.lancedb import LanceDBVectorStore

        return LanceDBVectorStore()
    else:
        raise ValueError(f"Unknown vector store type: {store_type}")


def get_vector_store() -> VectorStore:
    """
    FastAPI dependency that provides the configured vector store instance (singleton).

    This function is designed to be used as a FastAPI dependency:
        vector_store: VectorStore = Depends(get_vector_store)

    It can also be called directly for non-request contexts (e.g., background tasks).

    Returns:
        The vector store instance based on configuration.

    Raises:
        ValueError: If the configured vector store type is invalid.
    """
    global _vector_store_instance

    if _vector_store_instance is None:
        _vector_store_instance = _create_vector_store()

    return _vector_store_instance


def reset_vector_store() -> None:
    """
    Reset the vector store singleton instance.

    This is primarily useful for testing to ensure a fresh instance is created.
    """
    global _vector_store_instance
    _vector_store_instance = None


__all__ = [
    "VectorStore",
    "VectorRecord",
    "QueryResult",
    "get_vector_store",
    "reset_vector_store",
]